1. Field of the Invention
The present invention relates generally to the field of computer memory. More particularly, the present invention relates to the field of memory data masks.
2. Description of the Related Art
A typical computer system includes memory. A memory is used to store program code and data needed by that program code. The memory can be included on one or more boards of integrated circuits. Typically, the memory is coupled with a memory controller. The memory controller and the memory communicate over a data bus through pin connections.
Data masks are used to prevent selected data from being overwritten in memory. Accordingly, the memory controller can use data masks to mask specific data to allow partial writes to memory. Data mask bits may be associated with one or more bits of data. The associated data mask blocks writes to specific memory locations and allows writes into other specific memory locations. When a write to memory is performed, the selected data in memory that is masked remains in memory, and the selected data that is not masked is replaced by new data. If the memory controller does not use data masks, partial memory writes may take much longer. For example, the memory controller may approximate a partial write by reading an entire memory area, merging new data into it, and then writing back the entire memory area.
Currently, memory chips implement memory data masks by using separate pins for data mask bits and for data. This can greatly increase pin count. Increased pin count increases cost, package size, and, in some cases, die size. Using separate pins for data mask bits and for data provides no programming of registers with these mappings.